This invention pertains to a thermal hydrogenation and conversion process for solids-containing carbonaceous feed materials utilizing countercurrent flow of the feed and hydrogen to produce hydrocarbon gas and liquid products. It pertains particularly to such process wherein a thermal countercurrent flow hydrogenation reaction zone is used upstream of a catalytic hydrogenation reaction zone.
In thermal hydrogenation conversion operations on solids-containing carbonaceous feed material such as coal to produce lower boiling product liquids and gases, the feed material and hydrogen have generally both been introduced into the bottom of the reactor and both passed upwardly therethrough. However, reactor plugging difficulties sometimes occur due to heavy particulate mineral matter that forms in the reactor, settles and accumulates as solids agglomerates in the bottom of the reactor. Such accumulated solids in the reactor interfere with sustained process operations and are thus quite undesirable.
Accumulation of solids in the lower end of a hydrogenation reactor can usually be avoided by a periodic or continuous withdrawal of such solids. For example, U.S. Pat. No. 1,838,549 to Haslam and U.S. Pat. No. 1,876,006 to Krauch disclose processes for coal hydrogenation using stirred catalyst reactors to produce low boiling oil products, in which a liquid stream containing solids is withdrawn from the lower end of the reactors. Also, U.S. Pat. No. 3,488,278 to Nelson discloses a catalytic process for liquefying coal using continuous countercurrent extraction, in which ash and residue including solid catalyst particles are withdrawn from the reactor lower end along with minimal hydrocarbon liquid. U.S. Pat. No. 3,660,267 to Rieve et al discloses a non-catalytic coal hydrogenation process using an upflow reactor with contact solids being purged intermittently from the bottom end as needed. These alternative arrangements have deficiencies in practical large scale operations, involving high expense for stirring mechanisms, high expense in providing adequate liquid flow to assure sufficient time for solids to be dissolved in a liquefying solvent, difficulties in withdrawing high solids content material from the liquefying reactor, and operational upsets associated with the intermittent withdrawal of agglomerated accumulations from the liquefying reactor. U.S. Pat. No. 4,111,788 to Chervenak et al discloses a two-stage coal hydrogenation process using a thermal first stage reactor and catalytic second stage reactor, however, a counterflow arrangement for the coal feed and hydrogen in either reactor is not used.
Thus, a definite need exists for an improved thermal hydrogenation and liquefaction process for solids-containing carbonaceous materials such as coal and utilizing countercurrent flow of the feed and hydrogen so as to avoid the above difficulties associated with an undesirable accumulations of solids in the reaction zone lower end.